(1) Field of the Invention
The present invention relates to fluid dynamic forces in ships and in aeronautics. More particularly, the invention relates to vortex generation and dissipation for warship concealment and aircraft sustentation by movably mounted hull adjunct or fluid introducing elements.
(2) Description of the Prior Art
It is known to attempt to modify the wakes of aerial and marine vehicles to make the wakes less detectable or to reduce wake vortices which adversely affect nearby vehicles. Related wake and vortex reduction arrangements are also known for decreasing ship resistance and increasing air foil efficiency.
The following eight United States patents are representative of prior art for these purposes.
U.S. Pat. No. 5,088,433 issued to Osawa, et al. on 18 Feb. 1992 discloses decreasing the wave making resistance of a ship by adjustable fins mounted at the front of the ship and extending above and below the draft line. The fins are thus not applicable to underwater or aerial vehicles and do not directly affect wake vortices.
U.S. Pat. No. 5,158,251 issued to Taylor on 27 Oct. 1992 for “stemming tip vortex generation at its source” by discharging fluid span wise over a fluid foil tip to form a “Coanda curtain” which extends downwardly from the upper side of the foil and prevents vortex generating flow over the tip from its lower side. Tip vortices are thus prevented rather than being dissipated by counter vortices, and the Coanda effect is induced by a continuous flow at from one side of the foil.
U.S. Pat. No. 5,222,455, which issued on 29 Jun. 1993 to Furey, discloses a casing parallel to a ship hull to divert the hull boundary layer fluid to a pump which then expels the fluid alongside of and transversely from the hull. Fluid with the highest concentration of vorticity, which is the source of the most detectable vorticity features of a ship's wake, is thus removed from the wake. The disclosed system thus removes vortices from the wake rather than counteracting and dissipating the vortices.
U.S. Pat. No. 5,787,048 issued 28 Jul. 1998 to Sanford for ship wake signature suppression by projecting ultrasonic acoustic energy, in a range of 0.5 to 2.5 MHz, into the wake for coalescence of microbubbles which make the wake detectable. There is no mention of, or direct effect on, wake vorticity.
U.S. Pat. No. 5,791,875 issued to Ngo on 11 Aug. 1998 discloses the use of the Coanda effect to suppress free-stream air flow around the tip of a “lifting body” to attenuate or remove the tip vortex. Since, in a helicopter blade, high pressure can occur on either surface, an embodiment shown on FIG. 4 can direct the Coanda flow in either direction. However, in any one time the Coanda effect inducing flow is continuous and tip vortices are not subsequently dissipated by counter vortices.
U.S. Pat. No. 5,954,009 issued to Esmiol on Sep. 21, 1999 for a ship and submarine wake attenuation system having plates parallel to and outboard of a hull to reflect the wake back and forth between the plates and the hull to attenuate the wake. There is no mention of, or direct effect on, wake vorticity.
U.S. Pat. No. 6,082,679 issued to Crouch, et al. on 4 Jul. 4, 2000 for, as stated in column 1, a method and apparatus “addressing aircraft trailing vortices”. The only disclosed embodiment, which is in accordance with claim 4, moves a pair of existing control surfaces that are spaced span wise on an aircraft wing—aileron and flaperon, or aileron and spoiler—so as to excite instabilities of the vortices. As stated in column 7, the control surface motions are “preferably a waveform” with an aileron having positions “above the wing upper surface and below the wing lower surface” while a spoiler “can only move to positions above the wing upper surface.”
In Crouch, the generation of counter vortices is not mentioned. And, the use of a single moveable surface or multiple surfaces flapping toward or and from each other is not disclosed. While Crouch states in column 4 that one embodiment may be “a submarine with lifting surfaces that produce at least two vortex pairs.” no such embodiment is disclosed.
U.S. Pat. No. 6,513,761 issued on 4 Feb. 2003 to Huenecke discloses the use of a vortex generating flap to reduce a trailing vortex from an aircraft wing by generating a corresponding counteracting vortex imposed on the trailing vortex. As stated in Column 5 with reference to FIG. 6 where it is seen that the trailing vortices are about longitudinal axes, counter vortices 13 and 14 “are injected into the respective flap vortices 12B and 11B to thereby cause these flap vortices 11B and 12B to vibrate as indicated by the zigzag lines 11C and 12C, whereby the intensity of the respective flap vortices 11B and 12B is rapidly diminished or dissipated.” Also, as stated in Column 8, vortex generating flaps 9 and 10 may be in a “stationary extended position . . . or they can be operated dynamically by repeatedly extending . . . into the airstream . . . Moreover, the flaps on the [opposite wings] . . . may be . . . extended and retracted simultaneously . . . , or . . . one extended while the other is retracted . . . In both instances . . . longitudinal vibrations or asymmetric counter vortices are generated . . . suitable for accelerating the dissipating of the trailing vortices.”
In Huenecke, as shown in FIG. 6, the counteracting vortices 13 and 14 are axially parallel to the flap vortices 12B and 11B which are to be dissipated and the use of surfaces flapping toward and from each other is not mentioned.
The paper:
                Bandyopadhyay, P. R., Castano, J. M., Nedderman, W. H. & Donnelly, M. J.; “Experimental Simulation of Fish-Inspired Unsteady Vortex Dynamics on a Rigid Cylinder,”; ASME Journal of Fluids Engineering, Vol. 122, No. 2, pp. 219–238,of which the present inventor is a co-author, describes generation of propulsive vortices by flapping foils, these vortices being about axes generally transverse to the longitudinal direction of propulsion. However, there is no mention of these vortices in connection with longitudinal vortices or their modification.        